886 CHARLES PAuL ALEXANDER 
The tibiae are black, with a broad white band beyond the base. The 
second and third tarsal segments are pure white. The apically pubescent ’ 
wings (Plate XXX, 4) are characteristic of the genus. 
Faminy Rhyphidae 
The family Rhyphidae includes an apparently heterogeneous group 
of three subfamilies which, until a very recent date, were placed in three 
widely separated families of the nematocerous Diptera. The Rhyphidae 
comprise about fifty species, arranged in some seven genera. The family 
has long been held to contain only the genus Rhyphus and one or two 
closely allied exotic genera. In 1916, Edwards (1916) removed the 
genus Mycetobia from the family Mycetophilidae and placed it with the 
Rhyphidae. A critical study of the immature stages of the genus 
Trichocera now demonstrates that this group, likewise, should be placed 
in very close proximity to the Rhyphinae. In general appearance the 
three groups or subfamilies herein considered as comprising the Rhyphidae 
differ greatly, but the larvae of all members are so unmistakably related 
that there can be no question of the close phylogenetic relationship. 
The Trichocerinae have the more generalized wing venation, there 
being three branches to the sector and three to the media, and two 
distinct anal veins. The local species of Trichocera have the m-cu cross- 
vein punctiform or obliterated by a slight fusion of Cu on Ms. 
Trichocera trichoptera O. S., of the Western States, has the cross-vein 
very long and conspicuous. The second anal vein is long and subsin- 
uate in the subgenus Diazosma Bergr., but very short and recurved in 
the typical subgenus, in 7’. trichoptera being very short and reduced and 
narrowing the second anal cell. 
Edwards (1916) and Knab (1916) have recently shown the probable 
evolution of Mycetobia from the more generalized Rhyphidae such as 
Rhyphus and Olbiogaster. The most important venational feature to 
be considered is the reduction of the media in the Mycetobinae, but 
two branches persisting in Mycetobia and the vein tending to be evanescent 
in the Ethiopian-genus Mesochria. Species of Olbiogaster in some cases 
have the posterior branch of the media less strongly chitinized than 
the anterior fork, and probably indicate the manner in which the vein 
is reduced. An entirely comparable case is seen in the related family 
Ptychopteridae (comparing Ptychoptera and Bittacomorpha). In the 
